lamprophyllite
{{Short description|Ti-silicate mineral}}
{{Infobox mineral
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Lamprophyllite (named for its lustrous cleavage) is a rare, but widespread mineral Ti-silicate mineral usually found in intrusive agpasitic igneous rocks. Yellow, reddish brown, Vitreous, Pearly.{{Cite web|url=https://www.mindat.org/min-2315.html|title=Lamprophyllite}}
Lamprophyllite formula is (Sr,Ba,K,Na)2Na(Na,Fe,Mn)2Ti[Ti2O2(Si2O7)2[(O, OH,F)2 . Full isomorphic range between lampropyllite and baritollalpropyllite exist.{{Cite journal|last=Zaitsev V.A. Kogarko L.N.|date=2002|title=Compositions of Minerals of the Lamprophyllite Group from Alkaline Massifs Worldwide|journal=Geochemistry International|volume=40|pages=313–322}}
The general crystal-chemical formula for lampropyllite-related minerals can be written as A2[(M1)(M2)2(M3)X2] [[5] L2(Si2O7)2O2], where the contents of the O and H sheets are given in square brackets in this order and A = Sr, Ba,K, Na; M1 = Na, Mn2+; M2 = Na, Mn2+, Fe2+, Ca; M3 = Ti, Mn2+, Mg, Fe3+, Fe2+; L = Ti, Fe3+; X = OH, O, F.{{Cite journal|title=The crystal chemistry of lamprophyllite-related minerals: a review|journal = European Journal of Mineralogy|volume = 28|issue = 5|pages = 915–930|last1=Rastsvetaeva|first1=Ramiza K.|last2=Chukanov|first2=Nikita V.|date=2016-12-31|language=en|doi=10.1127/ejm/2016/0028-2560|last3=Aksenov|first3=Sergey M.|bibcode = 2016EJMin..28..915R}}
Lamprophyllite is monoclinic, The mineral also has an orthorhombic polytype{{Cite journal|last1=Krivovichev|first1=Sergey V.|last2=Armbruster|first2=Thomas|last3=Yakovenchuk|first3=Viktor N.|last4=Pakhomovsky|first4=Yakov A.|last5=Men'shikov|first5=Yuriy P.|date=2003-08-01|title=Crystal structures of lamprophyllite-2M and lamprophyllite-2O from the Lovozero alkaline massif, Kola peninsula, Russia|journal=European Journal of Mineralogy|volume=15|issue=4|pages=711–718|doi=10.1127/0935-1221/2003/0015-0711|bibcode=2003EJMin..15..711K|issn=0935-1221}} Unit-cell parameters mainly depend from the cationic composition in the interlayer position A{{Cite journal|last=Zaitsev|first=V. A.|date=May 2005|title=Numerical dependence of the unit-cell parameters of minerals of the lamprophyllite group on the cationic composition in the interlayer position|journal=Crystallography Reports|language=en|volume=50|issue=3|pages=379–381|doi=10.1134/1.1927593|bibcode=2005CryRp..50..379Z|s2cid=98166023|issn=1063-7745}} The crystal structures of the lamprophyllite-related minerals are based upon HOH modules consisting of a central octahedral O sheet sandwiched between two heteropolyhedral H sheets.{{Cite journal|title=The crystal chemistry of lamprophyllite-related minerals: a review|journal = European Journal of Mineralogy|volume = 28|issue = 5|pages = 915–930|last1=Rastsvetaeva|first1=Ramiza K.|last2=Chukanov|first2=Nikita V.|date=2016-12-31|language=en|doi=10.1127/ejm/2016/0028-2560|last3=Aksenov|first3=Sergey M.|bibcode = 2016EJMin..28..915R}}
Lamprophyllite melts incongruently (880 °C) with formation of titanium oxides: rutile, tausonite, freudenbergite. Syntetic lamprophyllite synthesis was crystallized from melt. Tewly formed lamprophyllite show higher Sr/Ba ratioi than in equilibrium melt.{{Cite journal|last=VA Zaitsev, LD Krigman, LN Kogarko|date=2004|title=Pseudobinare phase diagram lamprophyllite-nepheline|journal=Lithos|volume=EMPG-X special volume}}
